Tropism is when a plant changes its direction of growth in response to the environment.
Hope this helps you. Also if you go to Scott Forestmens book of science on page 110 is the lesson about that.
it is the specific movement of curvature in the response of any external stimulus.
the parallel of latitude 23°26ʹ north (tropic of Cancer) or south (tropic of Capricorn) of the equator.
:D